A masked Islamic State militant holding a knife speaks next to US journalist James Foley at an unknown location in this still image from an undated video posted on a social media website.

WASHINGTON - US President Barack Obama now admits that his decision to play a vacation round of golf immediately after addressing the murder of US journalist James Foley by Islamic State, was a mistake.

"I should have anticipated the optics," Obama said in an interview with NBC's "Meet the Press" on Sunday.

The president said that he had been forced to hold back tears when he spoke privately to the family of Foley, who was beheaded, but added that there was always the prospect of a "jarring" contrast between world events, and his own efforts to carve out a semblance of a normal life through recreation.

And he also admitted that sometimes his own performance in some of the more public rituals of the presidency was lacking.

"Part of this job, is also the theatre of it.

"It's not something that always comes naturally to me. But it matters. And I'm mindful of that," Obama said.

Obama was hammered in the press after being pictured smiling and enjoying his round of golf after making a public statement last month after Foley's death, while he was on vacation on the resort island of Martha's Vineyard.